The present invention relates to an illuminating method and apparatus in nuclear magnetic resonance inspection, and more particularly to an illuminating method and apparatus in nuclear magnetic resonance inspection in which a density distribution and a relaxation time of particular nuclei (e.g., a hydrogen nucleus and a phosphorus nucleus) of individual tissues in a living body are measured by utilizing a nuclear magnetic resonance phenomenon without invasion to obtain information for medical diagnosis.
Heretofore, X-ray CTs and ultrasonographs have widely been used as apparatuses for inspecting the internal structure of the human body in a non-destructive manner. In recent years, by utilizing a nuclear magnetic resonance phenomenon, it has become possible to obtain substantial medical diagnosis information that could not be provided by X-ray CTs and ultrasonographs.
For identifying signals from an object to be inspected (or a patient) separately for each of individual parts, an inspection apparatus utilizing a nuclear magnetic resonance phenomenon employs a method of applying a gradient magnetic field and a radio frequency magnetic field so as to make frequency and phase changes of the resulting resonance signal correspond to position information.
One most commonly used example of such a method is known as a spin-echo method. FIG. 13 shows a scanning sequence of the spin-echo method. In FIG. 13, a radio frequency magnetic field 45 and a gradient magnetic field 46 for slicing are applied to determine a particular slice plane, and a phase encode gradient magnetic field 47 and a frequency encode gradient magnetic field 48 are applied to obtain two-dimensional information in the slice plane, thereby measuring a nuclear magnetic resonance signal 49. To obtain one image, it is necessary to change a value of the phase encode gradient magnetic field 47 and repeat such a change 128 or 256 times. A repetition period 50 for this is generally set to a value in the range of about 0.3 second to about 3 seconds, and is an important parameter for a capability of tissue identification in view of a relaxation time of nuclear spins in the body tissues. Taking into account a signal time averaging scheme intended to improve the S/N ratio of the signal a train of scanning time values are distributed over a wide range from about 38 seconds to 20 minutes. Depending on the case, because inspection is conducted while shifting the slice plane or using a plurality of parameters, an inspection time for one patient may exceed one hour. If the patient moves during the inspection time an inconsistency occurs in position information of the image data and image artifacts appear on the reproduced image. As a result, a diagnosis capability may remarkably be lowered, or the positional relationship between images may be not clear.
When inspection is conducted using a nuclear magnetic resonance inspection apparatus, uniformity of a static magnetic field is required to be on the order of about 10 ppm so that image distortion will not be detrimental to diagnosis. While a superconducting magnet built up by solenoid coils can be used to achieve a static magnetic field with such a uniformity, it has a length almost twice its inner diameter and hence has a narrow, long tubular shape. This means that the patient is transported into a narrow, long inspection space within the superconducting magnet when inspected. Accordingly, there is a concern that the patient may feel uneasy in the closed and dark environment when transported into the inspection space under inspection. If the patient moves during inspection upon feeling uneasy, image artifacts appear and a diagnosis capability is remarkably lowered, as mentioned above.
Therefore, movements of the patient under inspection have conventionally been suppressed by not only fixing the patient's body by straps on the like so that locations to be inspected will not move during the long inspection time, but also by indicating the remaining scanning time to the patient to suppress a feeling of uneasiness felt by the patient.
As disclosed in JP-A-145643, it is known in the prior art to use optical fibers serving as light conductors to illuminate the inspection space with an even intensity of illumination and comfortable color light to make the patient free from anxiety. The above reference further suggests that to inform the patient of a period of time in which he or she must be at rest, the illumination may be turned on only for such a period of time, or that the illumination may be blinked as a sign for indicating the start of scanning.
Further, JP-A-3-47234 and JP-A-3-29638 disclose nuclear magnetic resonance inspection apparatuses which correspond to the prior art described above.